1. Field of the Invention
The present invention relates to a disk cartridge for rotatably accommodating a disk such as a WRITE ONCE type optical disk and so on.
2. Description of the Prior Art
A disk such as a WRITE ONCE type optical disk or the like is generally accommodated in a predetermined disk cartridge for protecting read and write errors of information signals caused by stain and scratch due to attached dust and damage due to contact with other disks and so on when the disk is not in service, i.e. when the disk is not loaded in a recording and/or reproducing apparatus. Such disk cartridge, as disclosed in Japanese Patent Publication No. 61-3015, is provided on its upper and lower halves with openings for exposing a portion of a signal recording portion of a disk accommodated in the cartridge and a chucking portion of the disk arranged at its central portion of the rotation. Also, disk supporting ribs are protrusively formed integrally with the cartridge halves, to avoid the contact of at least the recording portion of the disk with the inner walls of the cartridge halves, such that the disk is supported by the ribs at its non-recording portion.
In the disk cartridge constructed as mentioned above wherein the ribs formed integrally with the cartridge are used to support the disk, there is no shock absorbing effect on the disk so that there is a fear that the disk accommodated in the cartridge may be damaged by shock given thereto during transportation and so on, particularly if the base of the disk is made of synthetic resin such as polycarbonate. Thus, there is proposed, as disclosed, for example, in International publication No. W088/00385, that flexible shock absorbing pieces made e.g. of rubber plate or the like are arranged on the inner walls of the cartridge for supporting the disk so as to prevent the disk from being damaged by the above-mentioned shock.
To fix rubber plates as shock absorbing pieces on the inner walls of the cartridge, the rubber plate may be bonded with a bonding agent at predetermined positions on the inner walls of the upper and lower halves of the cartridge. Alternatively, pairs of protruded pins are formed at the respective predetermined positions and each rubber plate has a pair of horizontal leg portions integrated with its peripheral surface which repectively have bores at the positions corresponding to the pins, such that each pin is inserted into the bore of the rubber plate and the head of each pin is calked by ultra-sonic calking to thereby fix the rubber plate through the horizontal leg portion. The disk is thus supported by the rubber plates fixed on the inner walls of the upper and lower cartridge halves to thereby prevent damage caused by the aforementioned shock.
In the conventional disk cartridge constructed as described above wherein the rubber plates serving as the shock absorber are bonded with a bonding agent on the inner wall of the cartridge, if the bonding agent is excessively applied, it is not only extruded from the outer periphery of the rubber plate but also attached to the surface of the disk, with the result that the disk is stained by the extruded bonding agent. On the other hand, if the applied amount of the bonding agent is not sufficient, the rubber plate cannot be perfectly bonded and may be peeled from the inner wall of the cartridge by vibration of the disk, whereby the disk makes direct contact with the inner wall of the disk cartridge or the like. Thus, difficulties are encountered in controlling the applied amount and applied position of bonding agent for bonding the rubber plates.
In the case of fixing the rubber plates by calking the pins protruded on the inner wall of the disk cartridge halves, the horizontal leg portions for inserting the pin to be calked are also formed integrally with the rubber plate, thereby occurring variations or scatterings in the thickness of the leg portions. Since the scattering in the thickness of the leg portions cannot be suppressed in the molding thereof, the height of the calked pins is to be adjusted in the process of calking the pin in a manner that the height of the calked pin is lower than the disk receiving surface of the rubber plates. However, such adjustment is extremely difficult. Specifically, if the pin is calked so that the leg portion is pressed in order to lower the height of the pin, the entire disk receiving surface of the rubber plate is protrusively deformed, whereby the disk cannot be evenly supported with stability and consequently the disk may be deformed. Therefore, the pin must be calked so that a spacing is provided between the resulting calked pin and the leg portion of the rubber plate. Such work requires an extremely high accuracy and therefore working efficiency becomes lower.
In addition to the above-mentioned defects, since the leg portion of the rubber plate is integrated with the plate proper and lacks rigidity, torsion of the rubber plate caused by vibration and friction of the disk which is produced by shock applied to the disk when the disk cartridge is dropped or the like may arouse concern that the leg portion will be removed from the calking pin and consequently the rubber plate will be detached from the inner wall of the cartridge. The lack of rigidity in the leg portion makes it difficult to automatically mount the rubber plates on the cartridge halves, so that hand working must be introduced for the mounting which requires much more processes than the automatic mounting and therefore causes problems such as reduced manufacturing efficiency.